A liquid droplet ejecting head used with a liquid droplet ejecting apparatus, for example, an ink jet record head in a print field has nozzle openings communicating with pressure generation chambers. The pressure generation chamber receives energy of piezoelectric vibrators or heating elements and pressurizing liquid for recording so that the liquid for recording is ejected as droplets. Each nozzle opening has a taper part for efficiently converting ink pressurized in the pressure generation chamber into a liquid flow and a straight part for ejecting an ink droplet in a predetermined direction. Particularly, the nozzle opening affecting the droplet ejection performance needs to not Particularly, the nozzle opening affecting the droplet ejection performances needs to not only have an extremely minute opening diameter of several ten μm, but also be uniform in the same nozzle plate to ensure the droplet amount and ejection speed.
Such a nozzle opening of a nozzle plate is formed by a method of forming a through hole including a taper part by a punch from one face of press-workable metal, for example, a thin plate of stainless steel and lapping and removing burrs on an opposite face.
As disclosed in JP-B-1-26837, a method of forming a concave part on one face and a convex part on an opposite face by a punch and removing the convex part by grinding is adopted.
In such a punch, considering workability, the area which becomes a pore part of a nozzle opening is formed as a forward taper part with the tip side a little tapering and thus a pore part B of a nozzle opening A is also formed like a forward taper having an angle θ1 as shown in FIG. 4.
That is, to form a concave part on one face and a convex part on an opposite face by a punch tapering on the tip side or punch a through hole and remove a convex part by grinding or conduct a lapping step for removing burrs in the through hole. Since the concave part or the through hole has a taper angle of about two degrees, if the grinding amount changes on the order of 10 μm, hole diameter φ at the nozzle tip (usually, 30 μm) changes 0.7 μm, largely affecting the ejection characteristic of an ink droplet, particularly the ejection speed; this is a problem.
JP-UM-A-6-29724 discloses forming of a through hole by a punch formed with a reverse taper part on the tip side, but the invention described in the gazette is intended for decreasing the contact pressure with a workpiece in the punching step of the punch and is not intended for straightening the shape of a through hole. That is, an extremely large reverse taper angle is set so as not to come in contact with the punch as the through hole of the workpiece becomes elastically deformed during punching and after punching.
It is therefore an object of the invention to provide a nozzle plate suitable for a liquid droplet ejecting head for a liquid droplet ejecting apparatus including nozzle openings each having a pore part having a diameter of a stipulated size regardless of the grinding amount after punching.
It is another object of the invention to propose a method of manufacturing the nozzle plate.
It is still another object of the invention to provide a punch suited for manufacturing the nozzle plate.